Functional Modification Of PVDF Membrane By G-C₃N₄ And UIO-66 And Performance Of This Composite Membrane

Membrane treatment and photocatalysis technology have their own advantages in the treatment of water environmental pollutants.In this study,the two technologies are combined and put into the field of water treatment.On one hand,the uniform loading of photocatalyst mesoporous carbon nitride?MCN?and metal organic framework?MOF?material UIO-66 in ultrafiltration membrane PVDF is realized.On the other hand,the hydrophilic and photocatalysis characteristics of MCN and UIO-66 greatly improve the antifouling and permeability of PVDF membrane,which provide a new idea for the preparation and application of high-efficiency antifouling composite membrane.The main contents include the following four aspects:?1?MCN_x-MOF_y-PVDF hybrid membrane was prepared by immersion-precipitation phase transformation method.The crystal structure,molecular structure,micro morphology,hydrophilicity and membrane pore structure of MCN_x-MOF_y-PVDF membrane were characterized by XRD,FT-IR,XPS,SEM,contact angle tester,high-performance automatic mercury porosimeter,respectively.The results showed that the MCN and UIO-66 were successfully and evenly integrated in PVDF membrane.?2?The photocatalytic,self-cleaning and antimicrobial properties of MCN_x-MOF_y-PVDF membrane were tested.When the amount of MCN is 80 mg and the mass ratio of MCN and UIO-66 is 10:1,the photocatalytic performance is the best,and the degradation of 100 ml 2 mg/L CFX can be completed within 140 min.Through free radical capture experiment,·O₂^-is the main active substance for MCN_x-MOF_y-PVDF membrane to degradate CFX,while·oh and H⁺play a small role in the whole photocatalytic system.Among these free radicals,the membrane can degrade Rh B molecules which attached to the membrane surface under light irradiation,making the membrane has self-cleaning property.In addition,after 4 hours of photocatalysis in PBS solution containing 10⁷ CFU E.coli,3 log of E.coli was inactivated,indicating that MCN_x-MOF_y-PVDF membrane had certain antimicrobial property.?3?The application ability of MCN_x-MOF_y-PVDF membrane in sunlight irradiation and real environmental conditions was investigated.MCN₈₀-MOF₈-PVDF membrane was used to degrade CFX?100 ml 2 mg/L?under sunlight.The results showed that the efficiency of the MCN₈₀-MOF₈-PVDF membrane to degrade CFX remained 97.4%after five cycles of experiment under sunlight irradiation,indicating that the MCN₈₀-MOF₈-PVDF membrane prepared in this experiment has certain stability and practical engineering application value.?4?The hydrophilicity,permeability,rejection and antifouling of MCN₈₀-MOF₈-PVDFmembrane were evaluated.Compared with pristine PVDF membrane,the contact angle of MCN₈₀-MOF₈-PVDF membrane is reduced by 32.5%,the initial pure water flux is increased by 44%,while the rejection performance has no obvious attenuation.The flux recovery ratio?FRR?of MCN₈₀-MOF₈-PVDF improved about 28%,and the irreversible pollution R_ir of the membrane gets attenuation significantly,which prolongs the operation period of the membrane,indicating that the antifouling performance of MCN₈₀-MOF₈-PVDF composite membrane was greatly improved.